The present invention relates to antennas for communications devices and, in particular, to an adaptable directional antenna enabling selective application and positioning of the directional structure.
On typical hand-held communication terminals, there is provided a single omni-directional antenna, which can be a monopole, dipole or variants thereof. These antennas, however, have a fundamental limitation in that when held close to a user, the antenna beam pattern gets distorted and the available antenna gain is reduced.
There has been a move toward the use of directional antennas in an effort to minimize body loading effects. FIG. 1 illustrates a cross-section of a directional antenna for communications terminal applications including a radiator element mounted in a casing along with a director and a reflector. One example of a directional antenna is disclosed in U.S. Pat. No. 5,507,012, the disclosure of which is hereby incorporated by reference. The antenna structure helps to concentrate the electromagnetic (EM) energy in a certain direction, such as away from the user. By doing this, the antenna can achieve additional gains over conventional antennas. In this context, however, the position of the communications terminal relative to the user is not fixed, for example, when the user is speaking on the phone and when the user attaches the phone to a belt or the like, and the antenna is therefore not consistently working effectively for its designed purposes.